On an upcoming trip, I will be taking a desktop computer and monitor as checked luggage (on a United/Continental flight). What should I be aware of when doing this? What needs to be done to properly protect all the components? Are there any airline policies I should be aware of?
I personally would take some precautions. First of all, make a backup of your data. Leave on in your home and take another one with you so that you can use it in your destination place. Then when transporting a desktop computer, the most fragile part is almost always the hard disk drive. So I would dismount it if possible and take it into your cabin luggage. You could also do this for other sensible parts like for example other drives, the processor, or the RAM bars. This I would pack into anti-static bags and take it into the cabin.
The tower itself you can put into protected pc transporting bags like this one. This bag will be checked so that you can't smuggle and weapons or drugs. But you shouldn't normally fear that this will damage your computer.
And last but not least, you could also think about sending your computer with a carrier. I quote this from a message board:
A friend recently did this, flying from LON (London) to SYD (Sydney).
I went shopping with him and found a hard-shell suitcase. They're surprisingly light, and Samsonite has claimed theirs is "strong enough to stand on".
We then removed his harddisk drive. This is the most valuable and most fragile part of the computer. It's also feasible to do the same with the sticks of RAM and other parts, but the harddrive is the critical bit.
This was packed in an anti-static bag, and bubble wrapped, and I believe he actually took it on his carry-on to make sure he had it safe at all times.
Aside from that, you check the suitcase in just as per normal. I'd perhaps put some jerseys or other clothes in the case with the computer to try and give it just that extra bit of protection, and to prevent it from sliding around too much if it's not an exact fit.